Remove stalks and outer leaves of the cos lettuce and wash each leaf.
Cut the large leaves into half.
Chop the 4 tomatoes.
Peel the 2 avocados and chop them into J-inch cubes, add the 1 level tablespoon carrots, 1 level tablespoon radishes, diced, 2 tablespoons peeled and sliced cucumbers and the watercress.
Pour the dressing over and mix well.